Self-diffusivities of N-2, CH4, and Kr on 4A zeolite pellets by isotope exchange technique

The isotope exchange technique (IET) was used to measure equilibria and kin etics for adsorption of pure N-2, CH4, and Kr on a 4A zeolite sample. The i ntracrystalline self-diffusivities for these gases were measured under trul y isothermal conditions. The self-diffusivities of Kr and CH4 were smaller than that of N-2 by 2 and 1 order of magnitude, respectively. The self-diff usivity of N-2 was independent of its surface coverage but the self-diffusi vities of CIC and Kr increased with increasing coverages in the high-pressu re region. This effect was much more pronounced for Kr. The activation ener gies for self-diffusion of the gases increased in the order Kr > CH4 > N-2 while the isosteric heats of adsorption of these gases in the Henry's law r egion were very close. The activation energies were larger than the corresp onding isosteric heats of adsorption for each gas.